So the WiFi Calling connection either works or it doesn't = annoying. It changes throughout any given day

BT, whose router and broadband I have, suggested setting up the iPhone and router to access 5Ghz and 2.4Ghz signals. The former frequency works best most of the time. But sometimes the latter will work when the former doesn’t!

On the iPhone itself it shows the radiating signal graphic, either preceded by "No Service" or “iD WiFi Call”.

I have similar issues with my phone when trying to use it at home, to the extent that turning the wifi off when making a phone call seems to be the only way.My previous phone (or maybe the one before that) managed to make perfectly sensible calls via hotel wifi on more than one occasion. All iPhones, all reasonably up to date models for the time, and the OS is always the latest official version.

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"No matter how slow you go, you're still lapping everybody on the couch."

IME, the answer is 'not very well'.At work, the mobile signal is poor at best, but I have rock solid WiFi.The phone is usually on WiFi calling fallback.The success rate of calls is sub 50 percent.It rings, but the resulting call is silent.

When I was with BT Mobile Wi-fi calling was pretty solid, with the occasional blip. I switched to iD in jan and it’s never really worked well for me since. I’ve recently stopped getting it at all. I think it’s an issue with their end, but I haven’t done any debugging yet - I plan on doing some traffic capture and seeing whether the IPSec tunnels coming up properly.

Rather strangely, since my original post on 3rd August, every time I either, a) switch on my iPhone in the morning or b) return home from the other world which has mobile phone masts/coverage - the WiFi Calling has auto connected and worked without its usual well maybe sometimes attitude often changing its mind a few times during a single day.

Wifi calling has nowt to do with the SIM card. You can do it from a tablet if you want. On wifi calling it basically connects over the Internet to your mobile providers servers, logs you in with the account, and routes calls that way inbound and outbound. If your ISP deprioritises the telephony traffic or the servers the other end are shit, doesn't matter how good the wifi signal.

Wifi calling has nowt to do with the SIM card. You can do it from a tablet if you want. On wifi calling it basically connects over the Internet to your mobile providers servers, logs you in with the account, and routes calls that way inbound and outbound. If your ISP deprioritises the telephony traffic or the servers the other end are shit, doesn't matter how good the wifi signal.

Slightly pedantically, the SIM card is still required to authenticate you to the mobile provider. But other than that, as you say your device basically sends the data it would normally send over the radio interface down an encrypted tunnel over the internet to your mobile provider.

My experience would be that the early implementation of Wi-Fi calling was flawed, and the software would try to switch too much, resulting in dropouts. I found moving from the room that had my router in it to another one would caus a dropout, even though I have good mobile service throughout the house.

It is better now and I imagine that Apple have, in their normal way, tweaked the software to work without telling anyone.

Wifi calling has nowt to do with the SIM card. You can do it from a tablet if you want. On wifi calling it basically connects over the Internet to your mobile providers servers, logs you in with the account, and routes calls that way inbound and outbound. If your ISP deprioritises the telephony traffic or the servers the other end are shit, doesn't matter how good the wifi signal.

Also, WiFi (particularly with consumer-grade gear) is fundamentally poorly suited to this sort of thing, as it lacks any proper roaming capability, instead relying on the client to make arbitrary decisions about when would be a good time to reconnect. Needless to say, the timing is impeccably inconvenient.